---
title: "MAXPlanetary Gearbox System — REV-21-2100"
tags:
  - hardware
  - gearbox
  - planetary
  - REV
  - 2890
  - ion
type: hardware-spec
owner: 2890
status: active
sources:
  - "https://www.revrobotics.com/maxplanetary-system-kit/"
  - "https://docs.revrobotics.com/ion-build/motion/maxplanetary-system"
growth: tree
---

# MAXPlanetary Gearbox System — REV-21-2100

## Overview

Team 2890 uses the **MAXPlanetary** as their standard cartridge-based modular planetary gearbox. It's designed specifically for NEO-class motors (NEO, NEO 550, Falcon 500, 775) and allows rapid gear ratio changes without redesigning the entire mechanism.

## Key Features

- **Cartridge-based design** — swap gear ratios on the fly without rebuilding
- **27 gear ratios available** — 2:1 to 125:1 by stacking cartridges
- **Self-contained lubricated cartridges** — no re-greasing on swap
- **Three mounting options** — face mount, side mount, or stacked
- **1/2in hex output shaft** — compatible with standard FRC hex bearings
- **MAXSpline output** — integrates with REV ION system
- **Assembly front-to-back** — change ratios while mounted on robot

## Available Cartridges

| Cartridge | Ratio | Notes |
|-----------|-------|-------|
| 2:1 | 2:1 | **Reverses direction** — invert motor in code |
| 3:1 | 3:1 | |
| 4:1 | 4:1 | |
| 5:1 | 5:1 | |
| 9:1 | 9:1 | |
| 1:1 Brake | 1:1 | Sprag clutch — holds position, prevents backdriving |

**Combo math:** Stack cartridges for compound ratios. Example: 5:1 × 4:1 × 3:1 = 60:1 total reduction.

## Brake Cartridge

The **1:1 Brake Cartridge** uses a sprag clutch (torque diode) to mechanically lock output when motor is stationary. Automatically engages when output exceeds motor velocity.

**Specs:**
- Working torque: 16.95 Nm (150 in-lb)
- Static torque (no failure): 1,200 Nm (10,621 in-lb)
- Recommended as first cartridge (closest to motor) for maximum brake life

## 90 Degree Gearbox

The **MAX 90 Degree Gearbox** provides right-angle power transmission. Attaches to MAXPlanetary in 90° orientation for compact mechanisms in tight spaces. Through-bore design allows easy mounting.

## Connection to Training

**For students:** The MAXPlanetary teaches gear reduction fundamentals:
- **Why reduction?** — trade speed for torque. Motor has high RPM, low torque. Gearbox slows it down but multiplies force.
- ** planetary stages** — each cartridge adds one stage of reduction. More stages = more torque, less speed.
- **Ratio math** — multiply cartridge ratios to get total. 3:1 × 5:1 = 15:1.
- **Brake cartridge** — mechanical holding, not motor braking. Independent of motor state.

**Related training modules:**
- [[motor-basics]] — understanding motor output before gearbox
- [[swerving-modules]] — MK4i doesn't use MAXPlanetary (direct drive), but mechanisms do
- [[ion-build-system]] — integrates with REV ION structure
- [[2890-codebase-index]] — mechanism controllers that use gearbox output

## Source Links

- Product: https://www.revrobotics.com/maxplanetary-system-kit/
- Docs: https://docs.revrobotics.com/ion-build/motion/maxplanetary-system

## Notes

Chris typically uses MAXPlanetary on mechanisms (intake, shooter, climber) rather than drivetrain. Swerve modules have built-in belt reduction in the MK4i. For any mechanism that needs high torque at low speed — that's where MAXPlanetary lives.

Key concept for students: **gear reduction multiplies torque while dividing speed**. A 5:1 gearbox means the output turns 5× slower but the motor can push 5× harder.